Conventionally, as shown in Japan Patent Laid-open number 2006-184266 and Japan Patent Laid-open number 2009-42165, there is an exhaust gas analyzer for detecting and analyzing a predetermined component such as oxygen or nitrogen oxide contained in an exhaust gas in a duct that has an arrangement that a probe unit is directly inserted into a duct and mounted on the duct and the exhaust gas is sampled by the probe unit and a predetermined component such as, for example, oxygen or nitrogen oxide in the exhaust gas is detected.
Concretely the probe unit comprises a gas sensor having multiple gas introduction bores to introduce the gas into inside of the gas sensor and a sensor holder inside of which the gas sensor is held and that is arranged to be inserted in the duct so as to introduce the exhaust gas flowing in the duct into the gas sensor. A single calibration gas flow channel to supply a calibration gas to the gas sensor is formed in the sensor holder, and the calibration gas flow channel opens on an inner surface of a side wall surrounding the gas introduction bores of the gas sensor. With this arrangement, the calibration gas is supplied to the gas sensor by spraying the calibration gas over the gas introduction bores from the calibration gas flow channel so that the gas sensor is corrected.
However, since the calibration gas is supplied to the multiple gas introduction bores through a single calibration gas flow channel, there is a problem that it fails to sufficiently supply the calibration gas to inside of the gas sensor through the gas introduction bores. Especially, since the probe unit is arranged to be inserted inside of the duct, in case that the pressure in the duct is a negative pressure, there is a problem that it fails to sufficiently supply the calibration gas to the gas sensor because the probe unit is influenced by the pressure in the duct such that the calibration gas is pulled into inside of the duct prior to flowing into the gas introduction bores. Under this situation, in order to try to supply the sufficient calibration gas to inside of the gas sensor, there is also another problem that a consumption amount of the calibration gas increases.
In addition, it can be conceived that an opening of the calibration gas flow channel is arranged to face to one of the multiple gas introduction bores at a time of assembling the probe unit or the calibration gas flow channel is arranged to branch so as to face an opening of each branched channel to the gas introduction bore respectively in order to make it possible to sufficiently supply the calibration gas to inside of the gas sensor through multiple gas introduction bores, however, it is difficult to make the opening of the calibration gas flow channel face to the gas introduction bore in view of an assembling accuracy. Furthermore, with an arrangement where the calibration gas flow channel is branched, an arrangement of the sensor holder becomes complicated and jumboized, resulting in being unrealistic.